A centrifuge instrument is a device by which liquid samples may be subjected to centrifugal forces. The sample is carried within a member known as a centrifuge rotor. The rotor is mounted to a rotatable drive shaft that is connected to a source of motive energy.
Centrifuges currently employed in laboratories are generally operated by manual controls using various settings and procedures. A rotor control may be used to set the centrifuge to a specific sized or type of rotor. A temperature control and timer are also frequently used depending on the type of sample being tested. There are conventional power switches to manually turn the units on or off as needed. A physical key lock is commonly used to secure centrifuge access from operation. The change in Ke or back EMF, results in a change in the torque produced by the motor. This change in the Ke is caused by an increase in the motor temperature. This makes it difficult to accurately estimate the energy added to the rotor.
The present invention overcomes the prior art problems by measuring the back EMF and RPM simultaneously and calculating the Ke of the motor.